Very light on details, but this is interesting nonetheless - very interesting, and potentially one of the biggest things to have hit the operating systems business this decade. Bloomberg is reporting that Microsoft plans to announce Windows for ARM processors at CES in January 2011.

Sounds to me like a modified NT. It's not running Windows 2000, but it is definitely NT, albeit heavily customized. The article only states that it is not Windows 2000, but a different OS built specifically for the XBox. So a NT-based customized OS.